netdev - [PATCH] net/sctp: terminate rhashtable walk correctly

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Message-Id: <1469259755-18079-1-git-send-email-vegard.nossum@oracle.com>
Date:	Sat, 23 Jul 2016 09:42:35 +0200
From:	Vegard Nossum <vegard.nossum@...cle.com>
To:	Vlad Yasevich <vyasevich@...il.com>,
	Neil Horman <nhorman@...driver.com>
Cc:	linux-sctp@...r.kernel.org,
	"David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
	Vegard Nossum <vegard.nossum@...cle.com>,
	Xin Long <lucien.xin@...il.com>,
	Herbert Xu <herbert@...dor.apana.org.au>,
	stable@...r.kernel.org
Subject: [PATCH] net/sctp: terminate rhashtable walk correctly

I was seeing a lot of these:

    BUG: sleeping function called from invalid context at mm/slab.h:388
    in_atomic(): 0, irqs_disabled(): 0, pid: 14971, name: trinity-c2
    Preemption disabled at:[<ffffffff819bcd46>] rhashtable_walk_start+0x46/0x150

     [<ffffffff81149abb>] preempt_count_add+0x1fb/0x280
     [<ffffffff83295722>] _raw_spin_lock+0x12/0x40
     [<ffffffff811aac87>] console_unlock+0x2f7/0x930
     [<ffffffff811ab5bb>] vprintk_emit+0x2fb/0x520
     [<ffffffff811aba6a>] vprintk_default+0x1a/0x20
     [<ffffffff812c171a>] printk+0x94/0xb0
     [<ffffffff811d6ed0>] print_stack_trace+0xe0/0x170
     [<ffffffff8115835e>] ___might_sleep+0x3be/0x460
     [<ffffffff81158490>] __might_sleep+0x90/0x1a0
     [<ffffffff8139b823>] kmem_cache_alloc+0x153/0x1e0
     [<ffffffff819bca1e>] rhashtable_walk_init+0xfe/0x2d0
     [<ffffffff82ec64de>] sctp_transport_walk_start+0x1e/0x60
     [<ffffffff82edd8ad>] sctp_transport_seq_start+0x4d/0x150
     [<ffffffff8143a82b>] seq_read+0x27b/0x1180
     [<ffffffff814f97fc>] proc_reg_read+0xbc/0x180
     [<ffffffff813d471b>] __vfs_read+0xdb/0x610
     [<ffffffff813d4d3a>] vfs_read+0xea/0x2d0
     [<ffffffff813d615b>] SyS_pread64+0x11b/0x150
     [<ffffffff8100334c>] do_syscall_64+0x19c/0x410
     [<ffffffff832960a5>] return_from_SYSCALL_64+0x0/0x6a
     [<ffffffffffffffff>] 0xffffffffffffffff

Apparently we always need to call rhashtable_walk_stop(), even when
rhashtable_walk_start() fails:

 * rhashtable_walk_start - Start a hash table walk
 * @iter:       Hash table iterator
 *
 * Start a hash table walk.  Note that we take the RCU lock in all
 * cases including when we return an error.  So you must always call
 * rhashtable_walk_stop to clean up.

otherwise we never call rcu_read_unlock() and we get the splat above.

See-also: 53fa1036 ("sctp: fix some rhashtable functions using in sctp proc/diag")
See-also: f2dba9c6 ("rhashtable: Introduce rhashtable_walk_*")
Cc: Xin Long <lucien.xin@...il.com>
Cc: Herbert Xu <herbert@...dor.apana.org.au>
Cc: stable@...r.kernel.org
Signed-off-by: Vegard Nossum <vegard.nossum@...cle.com>
---
 net/sctp/socket.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/net/sctp/socket.c b/net/sctp/socket.c
index 67154b8..7f5689a 100644
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -4301,6 +4301,7 @@ int sctp_transport_walk_start(struct rhashtable_iter *iter)
 
 	err = rhashtable_walk_start(iter);
 	if (err && err != -EAGAIN) {
+		rhashtable_walk_stop(iter);
 		rhashtable_walk_exit(iter);
 		return err;
 	}
-- 
1.9.1